THE ELECTRIC MOTOR.
BARLOW’S SPUR WHEEL--DAL NEGRO’S ELECTRIC PENDULUM--PROF. HENRY’S
ELECTRIC MOTOR--JACOBI’S ELECTRIC BOAT--DAVENPORT’S MOTOR--THE NEFF
MOTOR--DR. PAGE’S ELECTRIC LOCOMOTIVE--DR. SIEMENS’ FIRST ELECTRIC
RAILWAY AT BERLIN, 1879--FIRST ELECTRIC RAILWAY IN UNITED STATES,
BETWEEN BALTIMORE AND HAMPDEN, 1885--THIRD RAIL SYSTEM--STATISTICS
ELECTRIC RAILWAYS AND GENERAL ELECTRIC CO.--DISTRIBUTION ELECTRIC
CURRENT IN PRINCIPAL CITIES.
Although the electric motor of to-day depends for practical value
entirely upon the dynamo which supplies it with electric power,
nevertheless the motor considerably antedated the dynamo. The genesis of
the electric motor began in 1821 with Faraday’s observation of the
phenomenon of the conversion of an electric current into mechanical
motion. In his experiment a copper wire was supported in a vertical
position so as to dip into a cup of mercury, while a small bar magnet
was anchored at one end by a thread to the bottom of the cup and floated
in the mercury in upright position. The mass of mercury being connected
to one pole of a battery, and the vertical wire to the other, it was
found that when the circuit was completed by clipping the wire into the
mercury, the floating bar magnet would revolve around the wire as a
center.
[Illustration: FIG. 26.--BARLOW’S WHEEL.]
In 1826 Barlow, of Woolwich, made his electrical spur wheel, Fig. 26,
and in 1830 the Abbe Dal Negro, in Padua, is said to have constructed a
sort of vibrating electrical pendulum, both of which devices were crude
forms of magnetic engines. Dal Negro’s machine, see Fig. 27, consisted
of a magnet A, movable about an axis situated about one-third of its
length, and the upper extremity of which was capable of oscillating
between the two branches of an electro-magnet E. A current being sent
into the electro-magnet, passed through an eight-cupped mercurial
commutator C, which the oscillating magnet controlled by means of a rod
_t_ and a fork F. When the magnet had been attracted toward one of the
poles of the electro-magnet this very motion of attraction acting upon
the commutator changed the direction of the current, and the magnet was
repelled toward the other branch of the electro-magnet, and so on.
[Illustration: FIG. 27.--DAL NEGRO’S ELECTRIC MOTOR.]
In 1828 Prof. Joseph Henry produced his energetic electro-magnets
sustaining weights of some thousands of pounds, and gave prophetic
suggestion of the possibilities of electricity as a motive power. In
1831 he devised the electric motor shown in Fig. 28, which is described
in Prof. Henry’s own words as follows:
“A B is the horizontal magnet, about seven inches long, and movable on
an axis at the center; its two extremities when placed in a horizontal
line are about one inch from the north poles of the upright magnets C
and D. G and F are two large tumblers containing diluted acid, in each
of which is immersed a plate of zinc surrounded with copper; _l m s t_
are four brass thimbles soldered to the zinc and copper of the batteries
and filled with mercury.
“The galvanic magnet A B is wound with three strands of copper bell
wire, each about twenty-five feet long; the similar ends of these are
twisted together so as to form two stiff wires _q r_, which project
beyond the extremity B, and dip into the thimbles _s t_.
[Illustration: FIG. 28.--PROF. HENRY’S ELECTRIC MOTOR.]
“To the wires _q r_ two other wires are soldered so as to project in an
opposite direction, and dip into the thimbles _l m_. The wires of the
galvanic magnet have thus, as it were, four projecting ends; and by
inspecting the figure it will be seen that the extremity _p_, which dips
into the cup _m_, attached to the copper of the battery in G,
corresponds to the extremity _r_ which dips into the cup _t_,
connecting, with the zinc in battery F. When the batteries are in
action, if the end B is depressed until _q r_ dips into the cups _s t_,
A B instantly becomes a powerful magnet, having its north pole at B;
this, of course, is repelled by the north pole D, while at the same time
it is attracted by C; the position is consequently changed, and _o p_
comes in contact with the mercury in _l m_; as soon as the communication
is formed, the poles are reversed, and the position again changed. If
the tumblers be filled with strong diluted acid, the motion is at first
very rapid and powerful, but it soon almost entirely ceases. By
partially filling the tumblers with weak acid, and occasionally adding a
small quantity of fresh acid, a uniform motion, at the rate of
seventy-five vibrations in a minute, has been kept up for more than an
hour; with a large battery and very weak acid the motion might be
continued for an indefinite length of time.”
Following Prof. Henry came Sturgeon’s rotary motor of 1832, Jacobi’s
rotary motor of 1834, Fig. 29, which had electro-magnets both in the
field and armature; Davenport’s motor of 1834, Zabriskie’s motor of
1837, in which a vibrating magnet converted reciprocating into rotary
motion; Davenport’s motor of 1837 (U. S. Pat. No. 132, Feb. 25, 1837),
Fig. 30; Page’s rotary motor of 1838, Walkley’s motor of 1838 (U. S.
Pat. No. 809, June 27, 1838); Stimson’s motor of 1838 (U. S. Pat. No.
910, Sept. 12, 1838); Page’s motor of 1839, Cook’s of 1840 (U. S. Pat.
No. 1,735, Aug. 25, 1840); Elias’ motor of 1842, invented in Holland;
Lillie’s motor of 1850 (U S. Pat. No. 7,287, April 16, 1850); the Neff
motor of 1851 (U. S. Pat. No. 7,889, Jan. 7, 1851), of which
illustration is given in Fig. 31, and Page’s motor of 1854 (U. S. Pat.
No. 10,480, Jan. 31, 1854). In 1835 Davenport constructed a small
circular railway at Springfield, Mass.
[Illustration: FIG. 29.--JACOBI’S ROTARY ELECTRIC MOTOR.]
In 1839 Prof. Jacobi, with the aid of Emperor Nicholas, applied his
electric motor to a boat 28 feet long, carrying fourteen passengers, and
propelled the same at a speed of three miles an hour. About the same
time Robert Davidson, a Scotchman, experimented with an electric railway
car sixteen feet long, weighing six tons, and attaining a speed of four
miles an hour. In 1840 Davenport, by means of his electric motor,
printed a news sheet called the _Electro Magnet and Mechanics’
Intelligencer_. In 1851 an electric locomotive made by Dr. Page in
accordance with his subsequent patent of 1854, drew a train of cars from
Washington to Bladensburg at a rate of nineteen miles an hour.
[Illustration: FIG. 30.--DAVENPORT MOTOR.]
[Illustration: FIG. 31.--NEFF MOTOR.]
[Illustration: FIG. 32.--WESTINGHOUSE ELECTRIC MOTOR.]
All these motors were operated by voltaic batteries, and on account of
the cost of the latter but little practical use of the electric motor
was made until the dynamo was invented. In 1873 an accidental
discovery led to the rapid practical development of the electric motor.
It is said that at the industrial exhibition at Vienna in that year, a
number of Gramme dynamos were being placed in position, and a workman
in making the electrical connections for one of these machines,
inadvertently connected it to another dynamo in active operation, and
was surprised to find that the dynamo he was connecting began to revolve
in the opposite direction. This was the clue that led to the important
recognition of the structural identity of the dynamo and the modern
type of electric motor. The dynamo and the electric motor then grew into
development together, and the same inventors who brought the dynamo to
its present high efficiency, produced electric motors of corresponding
principles and value. In the illustration, Fig. 32, is shown a modern
electric motor. It is a Westinghouse two-phase machine, of 300 horse
power, of the self starting induction type, designed to operate at a
speed of 500 revolutions per minute when supplied with two-phase
currents of 3,000 alternations per minute and 2,000 volts pressure.
[Illustration: FIG. 33.--SIEMENS’ FIRST ELECTRIC RAILWAY.]
The most important application of the electric motor is for street car
operation. The first electric railway was that of Dr. Werner Siemens, at
Berlin, in 1879, an illustration of which is given in Fig. 33. The first
electric railway in America was installed at Baltimore in 1885, and ran
to Hampden, a distance of two miles.
[Illustration: FIG. 34.--OVERHEAD TROLLEY CAR.]
[Illustration: FIG. 35.--UNDERGROUND ELECTRIC TROLLEY SYSTEM.]
The familiar overhead trolley cars, and the far superior conduit trolley
system, represent perhaps the largest use made of electric motors. The
motors are arranged under the cars in varying forms adapted to the
structure of the car. In the overhead trolley, shown in Fig. 34, the
current is taken from the overhead wire by a flexible trolley pole, and
in the conduit system a trolley known as a plow extends from the bottom
of the car through a narrow slot in the top of the conduit and makes a
traveling contact with the conductor rails within the conduit, which
carry the electric current. Fig. 35 is an end view of a street car of
the latter type, with the conduit and conductor rails in cross section.
The current goes from one rail to one bearing surface of the plow,
thence to the motor on the car and back to the other bearing surface of
the plow and the other conductor rail in the conduit.
[Illustration: FIG. 36.--THIRD RAIL SYSTEM ON THE N. Y., N. H. & H.
RAILROAD--FRONT END OF MOTOR CAR.]
A third system, which has supplanted to some extent the use of steam on
short line railways, is the so-called third rail system, of which an
example is seen in Fig. 36. A third conductor rail is placed between the
usual track rails, and from this conductor the current is taken by a
sliding shoe on the car, and carried to the motor and thence through the
car wheels to the track rails. To reduce danger from the live rail, the
third rail in some systems is made in sections, and, by an automatic
switching process as the car moves along, only the sections of the rail
beneath the car are brought into circuit, all other portions being cut
out.
The use of electric motors has greatly extended, cheapened, and
expedited the street car service. All the principal thoroughfares of
cities and even towns are now so equipped, and radiating suburban lines
extend for miles from the city, affording for five cents a pleasant and
cheap excursion for the poor to the green fields and fresh air of the
country.
[Illustration: FIG. 37.--ELECTRIC RAILWAY MOTOR, CLOSED.]
[Illustration: FIG. 38.--ELECTRIC RAILWAY MOTOR, OPENED.]
Figs. 37 and 38 show an electric motor used on street cars, as made by
the General Electric Company. Externally it presents the appearance of
some curious, uncouth, cast iron box, which, to the uninitiated, piques
the curiosity, and when opened adds no explanation of its real
character. In it, however, the electrician finds a most interesting
combination of metal and magnetism.
[Illustration: FIG. 39.--ELECTRIC LOCOMOTIVE OF B. & O. TUNNEL IN
BALTIMORE.]
In Fig. 39 is shown one of the most powerful electric locomotives ever
constructed. It was built in 1895 by the General Electric Company for
the Baltimore & Ohio Railroad, to draw trains through the long tunnel
from the Camden Street Station in Baltimore, for the purpose of avoiding
smoke and gas in the tunnel, which is 7,339 feet long. The locomotive
weighs ninety-six tons, or twenty-five tons above the average steam
locomotive. It was designed to draw 100 trains daily each way, moving
passenger trains of a maximum weight of 500 tons at thirty-five miles an
hour, and freight trains of 1,200 tons at fifteen miles an hour. It has
two trucks, and eight drive wheels of sixty-two inches diameter. There
are four motors, two to each truck, each rated at 360 horse power.
Other important applications of the electric motor are, the propelling
of automobile carriages, small boats, and fish torpedoes, operating
steering gear for ships, passenger elevators, rock drills in mines,
running printing presses, fans, sewing machines, graphophones, and in
all applications where space is limited and cleanliness a desideratum.
According to Mulhall there were in 1890 in the United States and Canada
about 645 miles of street railway operated by electricity. This about
concluded the first decade of the life of the electric railway. Some
idea of the rapid increase in this field may be had by the statement of
the same authority that there were in 1890, at the end of this first
decade, forty-five additional electric railroads in course of
construction, aggregating 512 miles of way, which nearly doubled the
previous existing mileage.
In 1898 it was estimated that there were in the United States 14,000
miles of electric railroads, with a nominal capital of $1,000,000,000,
and employing 170,000 men. In the same year a single electrical contract
was entered into between the Third Avenue Railroad and the Union Railway
Company of New York, acting as one, and the Westinghouse Electrical and
Manufacturing Company, amounting to $5,000,000. This was for the
electrical equipment of their respective railway lines, and is the
largest electrical contract ever made. The change in equipment from
other motive power to the electric is rapidly going on in all
directions, and the rapid succession of trains will doubtless cause it,
for passenger traffic on short lines, to eventually supersede steam.
The eighth annual report of the General Electric Company shows for the
year 1899 orders received for railway and other electrical equipment
amounting to $26,323,626; goods shipped, $22,379,463.75; profit on same,
$3,805,860.18. The growth of its business from 1893 to 1899 shows the
following per cent. of increase: In 1893, 36 per cent. above 1892; in
1894, 126 per cent. above 1893; in 1895, 10 per cent. above 1894; in
1896, 60 per cent. above 1895; in 1897, 60 per cent. above 1896; in
1898, 21 per cent. above 1897; in 1899, 51 per cent. above 1898.
The capitalization in electrical appliances in the United States in 1898
is estimated at $1,900,000,000, most of which is devoted to industries
in which the electric motor is used. The export of electrical apparatus
from this country amounts to more than three million dollars annually,
and it is said that there are eight times as many electric railways in
the United States as in all the rest of the world combined.
The use of electrical current in twelve principal cities in the United
States was distributed in 1898 as follows:
Lamps, arcs, and motors in sixteen candle power equivalents.
Boston 616,000
New York 1,718,000
Chicago 1,278,000
Brooklyn 322,000
Baltimore 224,000
Philadelphia 488,000
St. Louis 303,000
San Francisco 231,000
Buffalo 125,000
Rochester 184,000
Cincinnati 201,000
New Orleans 81,000
Boston makes the largest use of electrical current in proportion to its
population of any city in the world. Rochester is next. Both of these
cities employ in electrical units of 16 c. p. equivalents, more than one
electric lamp for every man, woman and child in their respective
populations.
The dynamo and the electric motor have together wrought this great
development. The dynamo takes mechanical power and converts it into
electrical energy, and the electric motor takes the electrical energy
and converts it back into mechanical power. Standing behind them both,
however, is the steam engine, and these three afford a beautiful
illustration of the law of correlation of forces. The force starts with
the combustion of coal under the boiler of the steam engine. When carbon
unites chemically with oxygen, it is an exothermic reaction that gives
off heat as correlated energy. The influence of heat on the molecules of
water in the boiler causes them, by repellent action, to assume the
qualities of an elastic gas, and this expanding as steam drives the
piston of the steam engine. The steam engine overcomes by force the
resistance existing between the dynamo’s field magnets and armature
coil, and sets up in the latter the correlated force of an electric
current, and the electric current, traveling to its remote destination
by suitable conductors, enters the coils of the electric motor in
reverse relation to that of the dynamo, and in producing the reverse
effect between the armature and field magnets, electrical energy is
converted back into mechanical power. It is not possible to obtain in
the electric motor the full equivalent of the dynamo’s current, nor in
the dynamo the full equivalent of the steam engine’s power, nor in the
steam engine the full equivalent of the chemical energy in the
combustion of coal. Loss by radiation, by conduction, by friction, and
by electrical resistance precludes this, but while there is loss in a
utilitarian sense there is no real loss, for force like matter, is
indestructible, and the proof of this universal law by Joule, in 1843,
constitutes one of the highest triumphs of philosophy and one of the
most important discoveries of the Nineteenth Century.